Three-dimensional virtual audio display employing reduced complexity imaging filters

Abstract

A three-dimensional virtual audio display method is described which includes generating a set of transfer function parameters in response to a spatial location or direction signal. An audio signal is filtered in response to the set of transfer function parameters. The set of transfer function parameters are selected from or interpolatated among parameters derived by smoothing frequency components of a known transfer function over a bandwidth which is a non-constant function of frequency. The smoothing includes for each frequency component in at least part of the audio band of the display, applying a mean function to the amplitude of the frequency components within the bandwidth containing the frequency component, and noting the parameters of the resulting compressed transfer function.

I claim: 
     
       1. A three-dimensional virtual audio display method comprising: generating a set of transfer function parameters in response to a spatial location or direction signal, and   filtering an audio signal in response to said set of transfer function parameters, wherein said set of transfer function parameters are selected from or interpolated among parameters derived by smoothing frequency components of a known transfer function in the frequency domain over a bandwidth which is a non-constant function of frequency wherein said smoothing includes for each frequency component in at least part of the audio band of the display, applying a mean function to the amplitude of the frequency components within the bandwidth containing the frequency component, and noting the parameters of the resulting compressed transfer function, wherein said smoothing comprises convolving said known transfer function H(f) with the frequency response of a weighting function W f  (n) in the frequency domain according to the relationship ##EQU4## where at least the smoothing bandwidth b f  and, optionally, the weighting function shape W f  (n) are a function of frequency.   
     
     
       2. A three-dimensional virtual audio display method comprising: generating a set of transfer function parameters in response to a spatial location or direction signal, and   filtering an audio signal in response to said set of transfer function parameters, wherein said set of transfer function parameters are selected from or interpolated among parameters derived by smoothing frequency components of a known transfer function in the frequency domain over a bandwidth which is a non-constant function of frequency wherein said smoothing includes for each frequency component in at least part of the audio band of the display, applying a mean function to the amplitude of the frequency components within the bandwidth containing the frequency component, and noting the parameters of the resulting compressed transfer function, wherein said smoothing comprises convolving said known transfer function H(f) with the frequency response of a weighting function W f  (n) in the frequency domain according to the relationship ##EQU5## where at least the smoothing bandwidth b f  and, optionally, the weighting function shape W f  (n) are a function of frequency.     
     
     
       3. A three-dimensional virtual audio display method comprising: generating a set of transfer function parameters in response to a spatial location or direction signal, and   filtering an audio signal in response to said set of transfer function parameters wherein said set of transfer function parameters are selected from or interpolated among parameters derived by smoothing frequency components of a known transfer function in the frequency domain over a bandwidth which is a non-constant function of frequency wherein said smoothing includes for each frequency component in at least part of the audio band of the display, applying a mean function to the amplitude of the frequency components within the bandwidth containing the frequency component, and noting the parameters of the resulting compressed transfer function, wherein said smoothing comprises convolving said known transfer function H(f) with the frequency response of a weighting function W f  (n) in the frequency domain according to the relationship ##EQU6## where at least the smoothing bandwidth b f  and, optionally, the weighting function shape W f  (n) are a function of frequency.     
     
     
       4. A three-dimensional virtual audio display method comprising: generating a set of transfer function parameters in response to a spatial location or direction signal, and   filtering an audio signal in response to said set of transfer function parameters, wherein said set of transfer function parameters are selected from or interpolated among parameters derived by smoothing frequency components of a known transfer function in the frequency domain over a bandwidth which is a non-constant function of frequency wherein said smoothing includes for each frequency component in at least part of the audio band of the display applying a mean function to the amplitude of the frequency components within the bandwidth containing the frequency component, and noting the parameter of the resulting compressed transfer function, wherein said smoothing comprises convolving said known transfer function H(f) with the frequency response of a weighting function W f  (n) in the frequency domain according to the relationship ##EQU7## where at least the smoothing bandwidth b f  and, optionally, the weighting function shape W f  (n)are a function of frequency.     
     
     
       5. A three-dimensional virtual audio display method comprising generating a set of transfer function parameters in response to a spatial location or direction signal, and   filtering an audio signal in response to said set of transfer function parameters, wherein said set of transfer function parameters selected from or interpolated among parameters is derived by smoothing frequency components of a known transfer function over a bandwidth which is a non-constant function of frequency and which is selected according to a criteria which limits the complexity of the resulting compressed transfer function, and noting the parameters of the resulting compressed transfer function wherein said set of transfer function parameters are derived by smoothing frequency components of known transfer functions over different bandwidths as a function of the spatial location or direction associated with the transfer function and as a function of the complexity of the transfer function; and wherein the bandwidth increases with increasing transfer function complexity.